/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.util;

import org.springframework.lang.Nullable;

import java.io.Serializable;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Simple customizable helper class for creating new {@link Thread} instances.
 * Provides various bean properties: thread name prefix, thread priority, etc.
 *
 * <p>Serves as base class for thread factories such as
 * {@link org.springframework.scheduling.concurrent.CustomizableThreadFactory}.
 *
 * @author Juergen Hoeller
 * @see org.springframework.scheduling.concurrent.CustomizableThreadFactory
 * @since 2.0.3
 */
@SuppressWarnings("serial")
public class CustomizableThreadCreator implements Serializable
{

    private final AtomicInteger threadCount    = new AtomicInteger(0);
    private       String        threadNamePrefix;
    private       int           threadPriority = Thread.NORM_PRIORITY;
    private       boolean       daemon         = false;
    @Nullable
    private       ThreadGroup   threadGroup;


    /**
     * Create a new CustomizableThreadCreator with default thread name prefix.
     */
    public CustomizableThreadCreator()
    {
        this.threadNamePrefix = getDefaultThreadNamePrefix();
    }

    /**
     * Create a new CustomizableThreadCreator with the given thread name prefix.
     *
     * @param threadNamePrefix the prefix to use for the names of newly created threads
     */
    public CustomizableThreadCreator(@Nullable String threadNamePrefix)
    {
        this.threadNamePrefix = (threadNamePrefix != null ? threadNamePrefix : getDefaultThreadNamePrefix());
    }

    /**
     * Return the thread name prefix to use for the names of newly
     * created threads.
     */
    public String getThreadNamePrefix()
    {
        return this.threadNamePrefix;
    }

    /**
     * Specify the prefix to use for the names of newly created threads.
     * Default is "SimpleAsyncTaskExecutor-".
     */
    public void setThreadNamePrefix(@Nullable String threadNamePrefix)
    {
        this.threadNamePrefix = (threadNamePrefix != null ? threadNamePrefix : getDefaultThreadNamePrefix());
    }

    /**
     * Return the priority of the threads that this factory creates.
     */
    public int getThreadPriority()
    {
        return this.threadPriority;
    }

    /**
     * Set the priority of the threads that this factory creates.
     * Default is 5.
     *
     * @see java.lang.Thread#NORM_PRIORITY
     */
    public void setThreadPriority(int threadPriority)
    {
        this.threadPriority = threadPriority;
    }

    /**
     * Return whether this factory should create daemon threads.
     */
    public boolean isDaemon()
    {
        return this.daemon;
    }

    /**
     * Set whether this factory is supposed to create daemon threads,
     * just executing as long as the application itself is running.
     * <p>Default is "false": Concrete factories usually support explicit cancelling.
     * Hence, if the application shuts down, Runnables will by default finish their
     * execution.
     * <p>Specify "true" for eager shutdown of threads which still actively execute
     * a {@link Runnable} at the time that the application itself shuts down.
     *
     * @see java.lang.Thread#setDaemon
     */
    public void setDaemon(boolean daemon)
    {
        this.daemon = daemon;
    }

    /**
     * Specify the name of the thread group that threads should be created in.
     *
     * @see #setThreadGroup
     */
    public void setThreadGroupName(String name)
    {
        this.threadGroup = new ThreadGroup(name);
    }

    /**
     * Return the thread group that threads should be created in
     * (or {@code null} for the default group).
     */
    @Nullable
    public ThreadGroup getThreadGroup()
    {
        return this.threadGroup;
    }

    /**
     * Specify the thread group that threads should be created in.
     *
     * @see #setThreadGroupName
     */
    public void setThreadGroup(@Nullable ThreadGroup threadGroup)
    {
        this.threadGroup = threadGroup;
    }

    /**
     * Template method for the creation of a new {@link Thread}.
     * <p>The default implementation creates a new Thread for the given
     * {@link Runnable}, applying an appropriate thread name.
     *
     * @param runnable the Runnable to execute
     * @see #nextThreadName()
     */
    public Thread createThread(Runnable runnable)
    {
        Thread thread = new Thread(getThreadGroup(), runnable, nextThreadName());
        thread.setPriority(getThreadPriority());
        thread.setDaemon(isDaemon());
        return thread;
    }

    /**
     * Return the thread name to use for a newly created {@link Thread}.
     * <p>The default implementation returns the specified thread name prefix
     * with an increasing thread count appended: e.g. "SimpleAsyncTaskExecutor-0".
     *
     * @see #getThreadNamePrefix()
     */
    protected String nextThreadName()
    {
        return getThreadNamePrefix() + this.threadCount.incrementAndGet();
    }

    /**
     * Build the default thread name prefix for this factory.
     *
     * @return the default thread name prefix (never {@code null})
     */
    protected String getDefaultThreadNamePrefix()
    {
        return ClassUtils.getShortName(getClass()) + "-";
    }

}
